The heart is a powerful symbol. Physiologically, it is essential to human life -- but so are the lungs and the liver, and they haven't become inexorably bound up with being alive/human and, most particularly, with being in love. I guess that the heart has gained its prime position because it's a piece of your insides whose workings you can be very aware of, moment by moment. When it speeds up and slows down, in situations of excitement, fear, or relaxation, it is very apparent to the owner. The power of love to make the heart beat faster isn't a cliche for nothing, it's true -- hence the heart being used as a shorthand for love. It's a shorthand now employed to such an extent that it's become a synonym for the word.
I must admit I'm very attracted to the idea of the suitor being turned to ice -- I can imagine him caught, transfixed, in a snowy woodland glade. Lit by thin winter sunshine, he's slowly turning transparent, sparkling and solid, from the feet up. If I wrote fantasy, I'd be tempted to borrow that one.